2 per minute is right around where you want to keep it. Anything more you should tune it down. But let it run for a while the hw errors tend to stop after it gets going for a bit. I have had stock s9's do 200 hw errors in an hour.

But I found once you get it running for a bit it tends to slow down.

725 isa what many were finding is best for 13.5 and 14 s9. Some 14th s9 were going pretty high.